SEQUENCE OF A PLANT CDNA FROM VICIA-FABA ENCODING A NOVEL RAN-RELATEDGTP-BINDING PROTEIN

A clone obtained from a broad bean (Vicia faba) developing cotyledon c DNA library contained the complete coding sequence of a polypeptide wi th very high homology to the small GTP-binding proteins Ran from human cells and Spil from yeast. These proteins belong to the ras superfami ly of proteins involved in different basic cellular processes. The Ran /Spil proteins interact with a protein bound to DNA (RCC1) and are tho ught to function in the regulation of the cell cycle. The amino acid s equence of the obtained plant Ran-homologue, designated Vfa-ran, is 74 % and 76% identical to Ran and Spil, respectively. The five functional , conserved domains of ras-related proteins are present in the Vfa-ran sequence. However, as in Ran/Spil the C-terminus of Vfa-ran is very a cidic and lacks the Cys motif for isoprenylation. Northern blotting re vealed a corresponding mRNA expression in broad bean roots, leaves, an d cotyledons with the highest level in roots.